/**
 * In-memory client & server cache helper for SIMS BPI 1.
 * Eliminates redundant fetches and sqlite queries on route switching.
 */

interface CacheEntry<T> {
  data: T;
  timestamp: number;
  ttl: number; // in milliseconds
}

class MemoryCache {
  private cache = new Map<string, CacheEntry<unknown>>();

  /**
   * Get data from cache. Returns undefined if expired or not found.
   */
  get<T>(key: string): T | undefined {
    const entry = this.cache.get(key);
    if (!entry) return undefined;

    const isExpired = Date.now() - entry.timestamp > entry.ttl;
    if (isExpired) {
      this.cache.delete(key);
      return undefined;
    }

    return entry.data as T;
  }

  /**
   * Set data into cache with a TTL (default: 5 minutes = 300,000 ms)
   */
  set<T>(key: string, data: T, ttlMs: number = 300000): void {
    this.cache.set(key, {
      data,
      timestamp: Date.now(),
      ttl: ttlMs,
    });
  }

  /**
   * Invalidate specific key or keys matching prefix
   */
  invalidate(keyOrPrefix: string): void {
    if (this.cache.has(keyOrPrefix)) {
      this.cache.delete(keyOrPrefix);
      return;
    }

    const keysToDelete: string[] = [];
    this.cache.forEach((_, key) => {
      if (key.startsWith(keyOrPrefix)) {
        keysToDelete.push(key);
      }
    });

    keysToDelete.forEach((key) => this.cache.delete(key));
  }

  /**
   * Delete specific key from cache
   */
  delete(key: string): void {
    this.invalidate(key);
  }

  /**
   * Clear all cache
   */
  clear(): void {
    this.cache.clear();
  }
}

export const appCache = new MemoryCache();